Method of making tetraorganolead compounds

ABSTRACT

A METHOD OF MAKING TETRAORGANOLEAD COMPOUNDS COMPRISING REACTING AN ORGANO HALIDE WITH A MAGNESIUMLEAD ALLOY OR A MAGNESIUM-SODIUM-LEAD IN THE PRESENCE OF CYCLOALKYLENE MONOETHER CATALYST AND/OR SOLVENT HAVING A FIVE-MEMBER RING, E.G., TETRAHYDROFURAN.

March 7, 1972 K', Q W|LL|AM5 E TAL l 3,647,838

METHOD OF MAKING TETRAORGANOLEAD COMPOUNDS Filed May l5,- 1969 AVAVAVAVNAVAVAVAVAVAVAVAVAVAVAVAVAVAVAVAVAVAVAVAVIAVAVAVAVAVAVAVAVAVAVAVAVAVAVAVA AVAVAVNAVAVAVAVAVAVAVAVAVAVAVAVAVAVAVAVAVAVAVAVAVNAVAVAVAVAVAVAVAVAVAVAVAVAVAVAVAVA A BAvanAVAvAvAvAvAvAvAvAvAvAvAvAvAvAvAvAvAvAvAvAvAvAvAvAvAvAnnnunuunnnvAvAvAvAvA NAVAVAVAVAVAVAVAVNAVAVAVAVAVAVAVAVAVAVAVAVAVAVAVAVAVAVAVAVNAVAVAVAVAVAVAVAVAVAVAVAVAVK@NAVA AVAVNVAVAVENAVAVAVAVAVAVAVAVAVAVAVAVAVAVAVAVAVAVAVAVAVAVAVAVAVAVAVAVAVAVAVAVIAVAVAVAVAVAVA B AVAVAVAVAVAVAVAVAVAVAVAVAVAVAVAVAVAVAVAVAVAVAVAVAVAVAVAVAVAVAVAVAVAVAVAVAVAVAVAVAVAVAVAVAVAVAVAVAVA C soDlUM l o MAGNESIUM United States Patent Otce 3,647,838 Patented Mar. 7, 1972 3,647,838 METHOD F MAKING TETRAORGANOLEAD COMPOUNDS Kenneth C. Williams and Wilford H. Thomas, Baton Rouge, La., assignors to Ethyl Corporation, New York,

Filed May 1s, 1969, ser. No. :524,765

im. cl. c07f 7/24 U.S. Cl. 260-437 R 16 Claims ABSTRACT OF THE DISCLOSURE A method of making tetraorganolead compounds comprising reacting an organo halide with a magnesiumlead alloy or a magnesium-sodium-lead in the presence of cycloalkylene monoether catalyst and/or solvent having a tive-member ring, eg., tetrahydrofuran.

BACKGROUND OF THE INVENTION Field of the invention The present invention relates broadly to the manufacture of tetraorganolead compounds. It particularly relates to the production of tetraalkyllead by the reaction of alkyl halides with magnesium-lead 0r magnesiumsodium-lead alloys in the presence of a cycloalkylene mono-ether catalyst and/or solvent. Tetrahydrofuran is a preferred catalyst.

Description of the prior art Tetraethyllead and tetramethyllead have been manufactured on a large scale for a number of years. Such organolead compounds are relatively expensive materials to manufacture and even slight improvements in yield are important commerically and economically.

The conventional method of making tetraalkyllead today involves a chemical reaction which may be expressed by the following equation:

Various tetraorganolead compounds are produced in accordance with this equation by substituting various organo halides for all or part of the alkyl chloride. The organo halides within contemplation include the alkyl halides containing from 1-5 carbon atoms. Alkenyl halides, notably vinyl halide, and aryl halides, notably phenyl halide, may also be employed. The term halide includes the chlorides, bromides and iodides. The chlorides, particularly methyl chloride and ethyl chloride, are preferred and superior results are achieved therewith.

Tetraorganoleads may be produced in either a batch or a continuous process. In either case, lead alloy and organo halides are repeatedly introduced to a reaction zone. Catalysts and/or solvents may also 4be introduced to the reaction zone. The reaction between the halide and the alloy produces the product tetraorganolead. All or a portion of the reaction mass is removed from the reaction zone and the product is recovered therefrom. Additional reactants are either periodically or continuously supplied to the reaction zone and a product is either continuously or periodically recovered therefrom.

Most of the lead introduced to the reaction zone is typically recovered from the reaction mass. This lead is usually remelted and used to make additional alloy. Such recovered lead is termed recycled lea In the processes illustrated hereinabove, the composition of the alloy is controlled to correspond substantially to NaPb, the reaction proceeds smoothly under proper conditions and tetraorganolead yields of about 2l percent by weight based on the lead input are obtained. It should be noted, however, that in the sodium lead reaction, less than one-fourth (Mt) of the lead originally present in the alloy is converted to tetraalkyllead. The remaining three-fourths (3A) or more of the original lead present is converted to finely divided metal considerably contaminated with the product. The presence of this large amount of unused lead in the autoclaves makes temperature control diicult, results in a low overall rate of product output, and necessitates a relatively large investment in equipment as compared with the more eicient processing of lead obtainable in practicing the present invention. Furthermore, the conversion of the -finely divided lead to a form suitable for use in making the sodium lead alloy is a hazardous and expensive operation. In view of the above, the manufacture of tetralkylleads from magnesium-lead alloys and certain of the alkyl halides has been considered because of the more eicient use of the lead in the process.

Several prior art U.S. patents, namely Nos. 2,535,235; 2,535,236; 2,535,237 and 2,000,069 all disclose various processes of making tetraalkylleads with magnesium-lead alloys. No catalyst was used in some of the processes and in others the reactions were catalyzed with aliphatic ethers such as methyl ether, ethyl ether, propyl ether and hexyl ether or aliphatic and aromatic amines. Alkyl bromide or iodide was frequently added to the catalyst. The processes never became commercial, apparently because of the need for magnesium and the necessary recovery of iodine or bromine, each of which were to be considered `adverse factors.

SUMMARY OF THE INVENTION It has been discovered that the magnesium-lead reaction with organic halides can be effectively improved wherein certain solvents such as tetrahydrofuran or other cycloalkylene monoether compounds are used as a catalyst. The solvent/catalyst acts to stabilize compounds presumed to be intermediates in the formation of lead alkyls from magnesium-lead or magnesium-sodiurn-lead alloys.

It is therefore an important `object of the present invention to provide a new and improved method of making tetraalkylleads from magnesium-lead or magnesium sodium-lead alloys and alkyl halides.

Another object of the present invention is to provide a new and improved method of making tetraorganolead compounds from magnesium-lead or magnesium-sodiumlead alloys and alkyl halides in the presence of a cycloalkylene mono-ether catalyst.

Still another object of the present invention is to provide a new and improved process of making tetraorganolead compounds by reactiug an alloy containing from about 71-88 percent lead, about 7-19 percent magnesium and about -10 percent sodium, by weight, with an alkyl halide, in the presence of a cycloalkylene catalyst.

It is a particular object of the present invention to provide a new and improved method of making tetramethyllead by reacting a magnesium-lead alloy with methyl chloride in the presence of tetrahydrofuran.

It is another important object of the present invention to provide a new and improved method of making tetraethyllead, wherein a magnesium-lead alloy is reacted with ethyl chloride in the presence of tetrahydrofuran.

A further object of the present invention is to provide a process of making lead alkyls wherein no by-product lead metal and magnesium are recovered for credit.

Other objects and advantages of the present invention will become readily apparent from a consideration of the description and claims hereinafter.

BRIEF DESCRIPTION OF THE DRAWING The drawing is a trilinear graph illustrating the composition of the alloys suitable for use in the instant invention.

DESCRIPTION OF THE PREFERRED EMBODIMENT In one preferred form of the present invention, a magnesium-lead alloy is reacted with an alkyl halide to form a magnesium halide and tetraorganolead according to the following equation:

Exemplary results have been obtained using methyl chloride in the above reaction to form tetramethyllead. The equation for this reaction is:

Yields as high as 77 percent have been obtained in the presence of tetrahydrofuran. A similar reaction using ethyl chloride to produce tetraethyllead has resulted in yields of percent.

The process is carried out at temperatures of 50 C. to 120 C., with preferred temperatures being in the range of 80 C. to 110 C. The optimum operating temperature is near 90 C.

In another preferred embodiment of the present invention, a magnesium-sodium-lead alloy is reacted with an alkyl halide in the presence of a cycloalkylene monoether to form a tetraorgano-lead. Methyl chloride and ethyl chloride have produced yields as high as 80 percent and 50 percent, respectively when using tetrahydrofuran as the catalyst and/or solvent.

Catalysts suitable for use in the instant invention are cycloalkylene mono-ethers having a lfive-member ring, i.e. tetrahydrofurans. Particularly useful catalysts are those compounds having the following formula:

wherein, R=H, an alkyl group having from 1-10 carbon atoms, or an aryl group.

Tetrahydrofuran produces optimum results. Some examples of suitable cycloalkylene mono-ethers are 2- methyl tetrahydrofuran, 3-rnethy1 tetrahydrofuran, 2,5-dimethyl tetrahydrofuran, 2-ethyl tetrahydrofuran, 2-butyl tetrahydrofuran, 2,5-dioctyl tetrahydrofuran, Z-phenyl tetrahydrofuran, and the like. Other suitable compounds include 2,2-diethyl tetrahydrofuran, 2-isopropyl tetrahydrofuran, 2-propyl tetrahydrofuran, and the like.

Optimum or preferred rango Operable range, percent percent Binary alloy:

8l-88 Pb The reaction of methyl and ethyl chlorides with magnesium-lead alloy has been studied in multiple autoclaves and in a two-liter autoclave. IIn such studies, methyl and ethyl chloride used were obtained from normal plant sources and were used without purification. Grignardgrade magnesium chips were used. Tetrahydrofuran (THF) was usually distilled from lithium aluminum hydride before use. In some of the two-liter autoclave experiments, THF was used without purification. Magnesium-lead alloy and magnesium-sodium-lead alloy were made by melting together with stirring the appropriate quantities of magnesium, lead and/or sodium metals. After solidiication, the alloy was broken into lumps by hammering on the steel pot and the lumps were ground to suitable size for use, less than 4mesh, in a dry box.

The multiple autoclave tests were carried out using a standard procedure. Comminuted magnesium-lead alloy and magnesium-sodium-lead alloy were weighed in samples of varying amounts, and each sample was sealed in a glass bulb. A dry, polished B1. inch steel ball was placed in each of the reaction vessels or steel bombs used in the tests. An alloy sample enclosed in a glass bulb was charged to a reaction vessel. A predetermined amount of methyl chloride or ethyl chloride was charged on the vessel in a proportion corresponding to about a six-fold excess of alkyl chloride over theoretical requirements. The necessary amount of THF and other additives tested were added to the bomb after the alkyl halide Was charged and just before the bomb was sealed. After the reactor was sealed, it was immersed in a constant temperature bath to raise the contents to reaction temperatures, and the bulb of alloy was broken by vigorous agitation of the autoclave and contents. After exposing the reactor contents to reaction temperatures for timed periods, the vessel was removed from the bath and cooled to terminate the reaction. The reactor was then opened, and the contents mixed in an organic solvent for extraction of TML or TEL product obtained, an aliquot of the liquid phase being removed and analyzed.

The two-liter autoclave was operated in a similar man- I ner. The alloy and the solvents or catalysts were charged into the autoclave which was then closed and heated to the desired feed temperature. The alkyl halide was then fed over about a l0 minute period. The autoclave heater was adjusted as necessary to maintain the reaction ternperature near the nominal operating temperature. Toluene was added to the charge in all runs to produce TML, the amount of toluene being suicient to give 80/20 TML-toluene at percent yield.

EXAMPLE I Various amounts of alloy were placed in multiple autoclaves and reacted with either -methyl or ethyl chloride in the presence of various amounts of tetrahydrofuran catalysts. The reactions were carried out at temperatures of 50, 70 and 94 C. Reaction times of 2-19 hours were used. For comparative purposes, several runs were made using no catalyst. In one instance, diethyl ether was used instead of tetrahydrofuran. THF was shown to be essential for the reaction of methyl chloride with MggPb. When no catalyst or when diethyl ether was used, no

product waslformed (Runs "1,2, Sand 4). `In runs employingl'TH-F, r*the highest yield was obtained in Run 15 andthe lowest'yield was'obtained'in Run `5."The results of these experiments are recorded hereinafter in Table l.

TABLE. 1...-MULrrPnn Aurocmvn emmene oF .Jnnonrpns vvITrI MAGNEKSIIJMJLEAD ALLOY G. oi THF L Timo Temp. Percent alloy '(ml) lRCl f (hrs) C.) yield 30 yNone MeCl '3 90 0 -30 None EtCl 3 90 0.7 30 None MeCl 3 90 0 30 l5 MeCl 3 90 0 v30 '2 MeCl 3 90 10.7 3o ..5 vMeC1 3 90 29.4 30 5 EtCl 3 90 18.0 5 MeCl 2 70 50.0 10` .5 MeCl 2 70 21.8 10 5 MeCl 2 50 12.6 10 5l MeCl 2 50 17.7 10 5 MeCl 2 50 20.4 10A 5 MeCl 2 94 60.8 10Il v5-MeC1 2 94 53.5 10 5. MeCl 2 94 43.2 30" 10 YMeCl 3 90 46.8 10 10 MeCl 2 70 34.8 10 10 MeCl 2 70 38.9 10 10 MeCl 2 70 47.3 30 14 MeCl 3 90 40.7 30 15 MeCl 3 70 44.2 30 15 MeCl 2 70 32.5 10v -15 `MeCl 2 70 26.9 19 15 MeCl 2 70 28.8 10l ..15 MeCl 2 70 25.8 "10 20 MeCl 2 70 22.9 .1 10 20..MeCl 2 70 25.8 30 40 MeCl 19 70 53.0 30y 40 MeCl 19 70 55.3

`EXALVIPLE n lA Isimilar .seriesof runs were made using a two-liter autoclave.. The` amount of THF required in the two-liter autoclave using a i150 g. charge of MgzPb alloy is in the range of 75-95 inl. This is invagrreement with the multiple autoclave results."When 95 ml. of THF is used with 1f50 g. of MgPb there is present 1 mole of THF per atom of magnesium. The results of these tests are set forth hereinafter in Table II.

TABLE IL TWO-LITER AUTOCLAVE TESTS OF REAC- TIONS OF METHYL CHLO RIDE WITH MAGNESIUM-LEAD- ALLOYS Cook TML Ml. Temp., time, yield, Run number THF C. hr. percent Methyl iodide was used ln lieu of met hyl chloride.

b Increased toluene.

No toluene was used.

d 1.7% sodium in alloy.

- 79% Pb, 15% Mg, 6% Na.

l 87% Pb, 7% Mg, 6% Na.

B Ethyl chloride used in lieu of methyl chloride; TEL prepared.

"From the examples herein, it is readily apparent that the TML yield is highly dependent on the amount of THF present. The optimum ratio appeared to be in the range of 0.5 to 1.0 ml. of THF per gram of MgzPb alloy.

l, EXAMPLEl n1 A. series-of alloys containing sodium in addition to magnesium and lead were tested in the .two-liter autoclave in the same manner as described in lEXample II. The composition of the alloys tested are set forth in Table III hereinafter. The lalloys were tested over a range of reaction temperatures and in making tetramethyllead and tetraethyllead. TI-[F was used as the reaction catalyst at the level previously determined to be about optimum, 50 percent by weight based on the alloy. Yields were based on the conversion of lead in the alloy to tetraalkyllead. The results of these tests are set forth in Table IV.

TABLE Ill.-SODIUM-MAGNESIUM-LEAD ALLOY COMPOSITIONS Wt. percent Atom percent Alloy code Mg Pb Na Mg Pb Na TABLE IV.-Y1ELDS USING SODIUM-MAGNESIUM-LEAD ALLOYS 9 See Table III for alloy compositions.

Some previous tests were made Iwherein no catalyst was used. The results of those tests are set forth in Table V.

TABLE 17.-REACTION TO MAKE TEL Alloy code Temp., Percent C. ld

e Sec Table Ill for alloy compositions.

From Tables III and IV it can readily be seen that alloy compositions A, B, C and E all gave TML yields of 75 percent or higher at 90 C. Alloys C and E gave TML yields of percent at 110 C. In the reaction to form TEL, alloy B gave the highest yield of 54.5 percent.

'I'he examples given herein are illustrative of the invention, and are not intended to limit the scope thereof. The reaction may be carried out in batch or in continuous operation. The manner of operation, as Well as the equipment used may be varied considerably within the scope of the invention.

What is claimed is:

1. A method of making tetraalkyllead comprising reacting a lower alkyl halide with a magnesium-lead alloy or a magnesium-sodium-lead alloy in the presence of a substantial amount of a cycloalkylene mono-ether catalyst and/ or solvent having a ive member ring, said catalyst being present in an amount of about 10 percent to about 150 percent by weight of alloy.

2. The method of claim 1, wherein said alloy comprises by weight, from about 7.19 percent magnesium, from about 7l-88 percent lead and from about 0.10 percent sodium.

3. The method of claim 1, wherein said alloy comprises by weight, from about l4-19 percent magnesium, from about 76-82 percent lead and about 0-5 percent sodium.

4. The method of claim 1, wherein said alloy comprises by weight, from about 18-19 percent magnesium and 81- 82 percent lead.

5. The method of claim 1, wherein said cycloalkylene mono-ether has the following formula:

and R=H, an alkyl group having from 1-10 carbon atoms, or an aryl group.

6. The method of claim 1, wherein said cycloalkylene mono-ether is tetrahydrofuran.

7. The method of claim 1, wherein said catalyst is present in an amount of about 0.5 to 1.0 ml. to about one gram of alloy.

8. The method of claim 1, wherein the reaction is heated from about 50 C. to about 120 C.

9. A method of making tetraalkyllead comprising reacting a lower alkyl halide with a magnesium-lead alloy in the presence of tetrahydrofuran in an amount of about l0 percent to about 150 percent `by weight of alloy.

10. A process for making tetramethyllead comprising reacting methyl chloride with a magnesium-lead alloy in the presence of tetrahydrofuran in an amount of about 10 percent to about 150 percent by weight of alloy.

11. A method of making tetraethyllcad comprising reacting ethyl chloride with a magnesium-lead alloy in the presence of tetrahydrofuran in an amount of about 10 percent to about 150 percent by weight of alloy.

12. The method of claim 9, wherein the tetrahydrofuran is present in an amount of about 0.5 to 1.0 m1. to about one gram of alloy.

13. The method of claim 9, wherein the tetrahydrofuran is present in an amount of about percent by weight of alloy.

14. The method of claim 9, wherein the tetrahydrofuran is present in an amount of about 50 percent t0 about percent by weight of alloy.

15. The method of claim 9, wherein the reaction is heated from about 50 C. to about 120 C.

16. The method of claim 9, wherein the reaction is heated to about C.

References Cited UNITED STATES PATENTS 2,535,191 12/1950 Calingaert et al. 260-437 R 2,535,192 12/1950 Calingaert et al. 260-437 R 2,535,235 12/1950 Shapiro 260-437 R 3,488,369 1/1970 Williams 260-437 R 2,859,232 11/1958 Blitzer et al. 260-437 3,062,853 11/1962 Pagliarini et al. 260--437 OTHER REFERENCES Shapiro: Advances in Chemistry Series, No. 23, Amer. Chem. Soc., Washington, D.C. (1959), pp. 290-8.

DELBERT E. GANTZ, Primary Examiner 40 H. M. S. SNEED, Assistant Examiner P04050 UNITED STATES PATENT OFFICE CERTIFICATE vOF CORRECTION Patent No. 5, 6247, 858 Dated March 7 1, 1972 Inventods) Kenneth C. Williams and Wilford H. Thomas It is certified that error appearsin the above-identified patent and that said Letters Patent are hereby corrected as shown below:

1 C-)olumn 5, line 7, reads ":'L'mportant", should read import Column il, line MO, reads v "onuthe should read. to the Column 5, llne 27, reads l'19 Hshouldlgead lOQ-- Column 5, llne 28, reads H25. H shou rea 5. Column 5, line 65, reads ll9 should read llO Signed and sealed this lst day of August 1972.

(SEAL) Attest:

EDWARD M.FLETCHER,JR. HUBERT GOI'TSCHALK Attestng Officer' Commissioner of' Patents 

